A need for securing overlapped rods together occurs in many different types of situations. Where the surfaces of the rods are fairly smooth, the securing can be done by welding, or by a variety of clamping devices that generate a jamming from the effect of wedges. U.S. Pat. Nos. 3,079,186 and 3,437,361 are illustrative of this type of device. Where the overlap portions of the rod have the usual threading common to bolts and nuts, devices are available for transferring tension through the rod overlap by maintaining the interengagement of the two adjacent thread systems. U.S. Pat. No. 3,039,800 is of this type, and U.S. Pat. No. 3,065,010 engages not only the threading of the rods, but also engages that of rods with the internal threading of a surrounding ring. Both of these patents are based upon conventional machine threading that permits positive interengagement of the threads such that when once interengaged, there is no relative axial freedom of movement of the rods with respect to each other.
Where the rods have surface irregularities according to a pattern substantially different from conventional machine threading, it still may be practical to interengage the surface irregularities for at least a participation in the transfer of tension across the overlap area. This form of rod configuration is frequently encountered in so-called "rebar", which is the reinforcing rod commonly embedded in concrete. A transverse clamping action is often sufficient to provide a satisfactory connection between rod sections, with the clamping serving both to hold the surface irregularities in engagement, and to positively interengage with these irregularities to transfer at least some of the axial stress. U.S. Pat. Nos. 3,771,884 and 4,080,084 are illustrative of this type of device. One form of rebar bears a somewhat superficial similarity to rod material that has machine threading. Where the latter has a V-shaped cross-section providing positive interengagement, the helical pattern of the rebar has a characteristic semi-circular cross-section that eliminates a corresponding positive interlock. The present invention is directed at providing a splicing device for this form of rebar.